Applied Mechanics and Materials Vols. 275-277

Abstract: Abstract. Magnetic fluid revolving sealing is widely used in modern industry. In the process of application, it is founded that the starting friction torque is very large, particularly at lower temperature. This problem has become a key factor restricting the application of magnetic fluid rotation sealing. In this paper, the mechanism of starting torque increase is analyzed, based on the change of microstructure and its viscosity. After analysis , such conclusion is obtained , which can be described: to a certain sealing structure, the type of magnetic fluid, size distribution of magnetic particles as well as the working condition concluding temperature, magnetic field gradient and the revolving velocity of shaft is the main influence factor of starting friction torque . It is very useful to reduce the starting friction torque.

Abstract: Design methodology of a rectangular variable geometry hypersonic inlet whose cowl lip is translatable along flow direction is clarified in current study and recommendation of key design parameters are given. Unsteady Reynolds-averaged Navier-Stokes (uRANS) calculation were carried out to investigate the feasibility and unsteady aerodynamic characteristics of this inlet. Results indicate that by stretching the movable lip of a model inlet upstream, mass flow rate will increases apparently due to the increases of inlet internal duct entrance area. Stretching the movable lip upstream will decrease CR of the model inlet which is favorable for the start or restart of the inlet from an unstarted status. The lip translating process is smooth and will not induce large amplitude flow disturbance within inlet duct. The movable lip is conducive to improve the aeropropulsive performance of the hypersonic inlet in wide flight range

Abstract: The effect of waving bottom on the fluid surface wave was investigated. Starting from the basic equations of potential flow theory and boundary conditions, we used the multiple scales perturbation method to deduce fluid surface waves satisfy the first-order approximate equation and second-order approximate equation. Under the second-order approximation, the fluid surface waveform was simulated with the Matlab in the presence of different waving bottom form. The results show that there are three solitary waves on the surface of the fluid. With the development of time, the amplitude of each solitary wave has not changed. It seems that they are not affected each other and propagate independently. So it suggests that the waving bottom is effective for maintaining surface wave energy balance income and expenditure in spreading process.

Abstract: Preconditioning technology is an effective method to simulate low Mach number flows, but the stability of the result is poor relatively. With the traditional preconditioning method on Roe’s scheme, the dissipation is too large in the boundary layer and extremely low-speed zone, and sometimes the result is unreasonable. Numerical experiments show the numerical dissipation of the scheme has a notable effect on low-speed flow numerical simulation with preconditioning method. A low-diffusion preconditioning Roe scheme by using an adjustable parameter in preconditioning Roe scheme to control the numerical dissipation and the adjustable parameter value rules are proposed. The low-diffusion preconditioning Roe scheme reflects the real physical dissipation in the extremely low-speed zone. In the region similar to the inflow speed, low-diffusion preconditioning Roe scheme can ensure the stability of the flow field. Numerical results show the efficiency of the new scheme and the low Reynolds number steady solutions of viscous flow past a circular cylinder are satisfied.

Abstract: This paper describes a numerical method for solving the unsteady Euler equation at any speed. In the process of calculating Euler's equation, the control equation in orthogonal curvilinear coordinate system is discretized by the finite -volume scheme based on the center-difference method, and convection flux used Jameson central deference scheme was solved at every pseudo time step, and the Runge-Kutta method, dual-time algorithm and the implicit LU-SGS add preconditioning algorithm are used for time-marching. For obtaining the numerical solution of two-dimensional unsteady flow around a cylinder and the flow of the Convex Hull, finding that the calculated results agree well with literature values and theoretical analytical solution.

Abstract: The accurate prediction of the dynamic reserves of gas reservoirs is the important research content of the development of dynamic analysis of gas reservoirs. It is of great significance to the stable and safe production and the formulation of scientific and rational development programs of gas reservoirs. The production methods of dynamic reserves of gas reservoirs mainly include material balance method, unit pressure drop of gas production method and elastic two-phase method. To clarify the characteristics of these methods better, in this paper, we took two typeⅠwells of a constant volume gas reservoir as an example, the dynamic reserves of single well controlled were respectively calculated, and the results show that the order of the calculated volume of the dynamic reserves by using different methods is material balance method> unit pressure drop of gas production method >elastic two-phase method. Because the material balance method is a static method, unit pressure drop of gas production method and elastic two-phase method are dynamic methods, therefore, for typeⅠwells of constant volume gas reservoirs, when the gas wells reached the quasi-steady state, the elastic two-phase method is used to calculate the dynamic reserves, and when the gas wells didn’t reach the quasi-steady state, unit pressure drop of gas production method is used to calculate the dynamic reserves. The conclusion has some certain theoretical value for the prediction of dynamic reserves for constant volume gas reservoirs.

Abstract: Convective heat transfer of non-Newtonian power-law fluids in a microchannel is investigated. The governing parameters include the flow behavior index, the length scale ratio (ratio of Debye length to half channel height), the Joule heating parameter (ratio of Joule heating to surface heat flux), and the Brinkman number. Analytical expressions are presented for velocity and temperature profiles, as well as the Nusselt number. The flow and heat transfer parameters can be obtained by numerical integrations of the analytical expressions. The dimensionless temperature distribution across the microchannel and the fully-developed Nusselt number are illustrated for a wide range of governing parameters.

Abstract: Numerical investigation was conducted on a typical two-dimensional hypersonic inlet to study the influence of unforced boundary layer transition affected by compression ramp geometric parameters on the inlet performance. The numerical results show that the transition onset location on the compression ramp can be delayed by filleting the ramp intersection, and also the inlet's performance obviously improves when the transition onset location is delayed. Compared with full turbulent situation, when the boundary layer transition occurs, the unstart of the inlet is significantly mitigated, the heat transfer rate on the compression ramp decreases, both the total pressure recovery coefficient and mass flow rate increase at both design and off-design points. But the static pressure distribution along the ramp is fairly independent of the varieties of boundary layer.

Abstract: A 2D Lattice Boltzmann model for a blood vesssel under rolling manipulation(RM) was presented. The influence of rolling frequency and stenosis coefficient on blood flux, wall shear stress and flow velocity was given by the numerical simulation based on lattice Boltzmann method . It is found that increasing RM frequency can not always increase the flux. There is a proper RM frequency for maximum flux.When the maximum stenosis coefficient increases,the change range of flux and wall shear stress will increase. The rolling massage can also change flow velocity in different sections of blood vessel.

Abstract: In this work, a ghost cell immersed boundary method is applied to the numerical simulation of a uniform flows over a circular cylinder and two circular cylinders in tandem arrangement. The Navier-Stokes equations are solved using an implicit fractional step method employed on collocated arrangement variables. Immersed boundary method permit the use of structured Cartesian meshes to simulate flows involving complex boundaries. The shedding of vortices and flow interference between two circular cylinders in tandem arrangement are investigated numerically. The calculations are validated against the experimental and numerical results obtained by other researchers to prove the accuracy and effectiveness.